1. Field of the Invention
The invention relates to a fuel cell system.
2. Description of the Related Art
In recent years, vehicles provided with fuel cell systems have continued to be put into practical use. A fuel cell system typically has, in addition to a fuel cell stack that generates electricity by an electrochemical reaction between hydrogen and oxygen, a gas-liquid separating device that separates hydrogen off-gas discharged from the fuel cell stack from water produced by the electrochemical reaction in the fuel cell stack, and a circulating pump for supplying the hydrogen off-gas that has been separated from the water to the fuel cell stack again, and the like.
The circulating pump in the fuel cell system is often made of metal, while the gas-liquid separating device is often made of resin or the like to reduce weight. Japanese Patent Application Publication No. 2008-66087 (JP-A-2008-66087), for example, describes technology related to a gas-liquid separating device in a fuel cell system.
In many fuel cell systems, the fuel cell stack is connected to an insulating gas-liquid separating device, and a member that forms a passage of the circulating pump is connected to the downstream side of a member that forms a passage of the gas-liquid separating device. This conductive circulating pump may be connected to a ground such as a frame of a vehicle.
In such a fuel cell system, if electrical conduction is established between a high voltage portion of the fuel cell stack (such as a flow passage inside a separator that forms part of the fuel cell stack) and the circulating pump via water that has been produced, the fuel cell stack will short.
Incidentally, this kind of problem is not limited to a gas-liquid separating device of a fuel cell system and a circulating pump that is connected to the gas-liquid separating device. The same problem typically exists when there is an insulating passage member through which produced water and off-gas pass, and a conductive passage member that is connected to that passage member.